1. Field of the Invention
This invention relates to an apparatus for recording/reproducing information by utilizing certain electric phenomena that occur when a voltage is applied between a probe and a medium to make them approach each other. More particularly, it relates to an information processing apparatus for recording/reproducing information by measuring the electric current running between a probe and a medium and detecting changes in the electric current signal.
2. Related Background Art
As a result of the development of scanning probe microscope (hereinafter referred to as SPM) that allows the user to directly observe the surface of an object or the electronic structure near the surface of an object by making a probe and the object approach each other and utilizing certain physical phenomena (a tunneling phenomenon, an atomic force, etc.) that occur between them, it is now possible to directly observe various physical volumes with an enhanced level of resolution for a real space image regardless if the volume is monocrystalline or noncrystalline.
From the industrial point of view, efforts have been paid for developing novel information recording/reproducing apparatus, using a recording medium in the form a layer as such an object and exploiting the high resolution of the SPM adapted to observe an atom or a molecule. Japanese Patent Applications Laid-Open Nos. 63-161552 and 63-161553 disclose such apparatus.
An information recording/reproducing apparatus of the type under consideration is often adapted to process a plurality of probes simultaneously (multi-processing) in order to improve the data transfer rate of the apparatus.
Thus, researches have been made for applying an existing semiconductor process to the process of preparing probes.
For example, in order to realize a data transfer speed of about 200 Mbps, a total of 2,000 probes have to be used if each probe shows a transfer speed of 100 kbps. While 2,000 probes may be produced on a same and single substrate by utilizing a known semiconductor process, they will often have to be arranged two-dimensionally on the surface of the substrate, which will be referred to as probe substrate hereinafter.
When arranging probes two-dimensionally, the medium surface and the probe substrate have to be rigorously held in parallel with each other in order to keep all the probes separated from the medium at a distance good for their mutual interaction.
The parallelism between them can be achieved by arranging three or more than three measuring systems on the probe substrate for measuring the distance between the probe substrate and the recording medium and collecting distance information from the systems.
If conventional optical lever type AFMs are used for measuring the distance at a plurality of points, each of them requires an optical detection system so that the entire arrangement of simultaneously measuring the displacements of the plurality of probes will be a very complicated one, which can be problematic particularly when the probes are to be integrally prepared.
On the other hand, the piezoresistor technology has become available for measuring a displacement of an object. With this technology, the change in the electric resistance of a semiconductor due to its strain is detected by way of the corresponding strain of a displacement detection system that typically comprises a cantilever as disclosed in Japanese Patent Application Laid-Open No. 5-196458. When such a displacement detection means is used, there is no need of employing conventional optical lever type AFMs and optical detection systems. Thus, such a means is particularly advantageous for integrally producing a plurality of displacement detection probes on a substrate because only the change in the resistance has to be detected with such a means.